Mobile phone operator Everything Everywhere will appoint financial advisers within weeks to sell an estimated £425m chunk of its airwaves.

The company had previously suggested the spectrum was worth so little that it would forfeit any proceeds by handing it back to Ofcom, the telecoms regulator, to sell.

The divestment, which represents a quarter of Everything Everywhere's 2G spectrum that is used for voice calls, was ordered by the European commission after the creation of the UK's largest mobile phone network through the merger of Deutsche Telekom's T-Mobile and France Telecom's Orange.

The commission says the sell-off must take place before the end of 2012 when the UK government holds its own 4G auction, which would release capacity for networks to create super-fast mobile internet and could raise £3bn for the Treasury.

A spokeswoman for Everything Everywhere said: "I can confirm that Everything Everywhere is looking to appoint external advisors to provide us with independent professional advice on the sale." An appointment is likely to take place around Christmas or early in the new year.

The airspace will be used for 4G superfast mobile internet. Based on prices paid in recent Italian and Swedish 4G auctions, Daniel Gleeson, a research analyst at IHS Screen Digest in London, calculates that Everything Everywhere's 30 Megahertz of airwaves could be worth £425m.

"The implication of their appointing advisers is that they are looking to try to sell it themselves, they don't want to just hand it back to Ofcom," said Gleeson. "Spectrum is valuable because it is the lifeblood of the mobile internet. It is incredibly important with more and more smartphones coming onto the networks."

As mobile networks are forced to carry ever-larger amounts of data, those with the most spectrum will be able to offer the fastest speeds to the highest number of customers.

Everything Everywhere pays a licence fee of £33m a year to the government for this 30 Megahertz chunk. Prices paid in the 4G auction will be used to calculate higher annual licence fees, and the company had argued that this would reduce the price rivals might be willing to pay to almost nothing.

The recruitment of advisers suggests Everything Everywhere has instead decided that there could be significant proceeds and that it should have the option of retaining control of the sale.

Vodafone and O2 are considered the most likely buyers, although Everything Everywhere may prefer to see what is a potentially valuable asset handed to a smaller competitor such as Three, which has market share of about 10%.

Everything Everywhere may still seek permission from the European commission to sell 20 Megahertz rather than the current requirement of 30.

The company has promised to re-invest any funds raised from the spectrum sale in its network.

It is also in the process of raising money to repay part of a £1.25bn loan from its parents, and has lined up seven banks to borrow £875m, in what is expected to be one of the largest corporate bank loans arranged in the UK this year. The banks lending money to Everything Everywhere are HSBC, Royal Bank of Scotland, Morgan Stanley, Barclays, Lloyds, Bank of Tokyo Mitsubishi and JPMorgan. The company may tap the bond market next year to raise further funds for investments including acquiring spectrum in the 4G auction.